How does reforestation reduce or reverse the effects of desertification in an area?
Tree tops absorb solar radiation, leading to a warmer canopy.
Trees can be habitats for many small herbivores and carnivores.
Trees can reduce the loss of soil and increase the humidity of an area.
Trees sequester carbon from the atmosphere as sugars, starches, and
cellulose in their tissues.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.